[Maintenance Configuration API] The service API would lower the key of tags

Hi team,

We found that the service API (Maintenance Configuration API) would lower the key of tags. So could you double confirm whether lowering the key of tags is expected?

Request payload:
```
PUT https://management.azure.com/subscriptions/xx-xxx-xx-xx/resourceGroups/acctestRG-maint-test01/providers/Microsoft.Maintenance/maintenanceConfigurations/acctest-MCtest01

{
"location": "westeurope",
"name": "acctest-MCtest01",
"properties": {
"extensionProperties": {},
"maintenanceScope": "SQLDB",
"namespace": "Microsoft.Maintenance",
"visibility": "Custom"
},
"tags": {
"Env": "Test"
}
}
```

API response:
```
```
GET https://management.azure.com/subscriptions/xx-xxx-xx-xx/resourcegroups/acctestRG-maint-test01/providers/Microsoft.Maintenance/maintenanceConfigurations/acctest-MCtest01?api-version=2021-05-01

{
...
"tags": {
"env": "Test"
},
...
}
```
```

Start by locating the Maintenance Configuration API specification in this repository and inspect how the tags property is defined. Compare the reported PUT request and GET response with the specification and determine whether key casing is documented or requires clarification. Done means the expected behavior is established and the specification or issue guidance reflects that decision.

Written by the indexing model from the issue text.